Exposure control device for a camera

ABSTRACT

An exposure control device for a camera comprising: an electronic shutter control device for shutter actuation, a brightness indicator circuit for indicating and warning insufficient brightness of an object being photographed, and exposure measuring circuit connectable to said brightness indicator circuit and flash ready indicator for a flash exposure, whereby an indicator in said brightness indicator circuit instructs a camera operator to use a flash device and said flash indicator assures camera operator to get a correct flash exposure.

I Umted States Paten 1151 3,678,828

Mashimo et a1. 14 1 July 25, 1972 154] EXPOSURE CONTROL DEVICE FOR A3,374,718 3/1968 Hochreiter .95/10 c CAMERA 3,316,445 4 1967 Ahrons315/241 P 3,273,478 9/1966 Kinder ..95/1 I R [721 :F 3,393,620 7 1968Reiche et al. ..95/11 R Japan 3,418,904 12/1968 Wick a al... 895/1 1.5 R[73] Assignee: Canon Kabushiki Kaisha, Tokyo, Japan 3,424,071 1/1969Schwahn ,.95/l 1.5 R

[22] Filed: 1970 Primary Examiner-Samuel S. Matthews 2 1 App], 32,374Assistant Examiner-Robert P. Greiner Attorney-McGlcw and Toren [30]Foreign Application Priority Data [57] ABSTRACT Oct. 27, Japan 4 An expoure control de ice o a Camera co p sing an elec tronic shutter controldevice for shutter actuation, a [52] Cl "95/11 95/ gl gg i brightnessindicator circuit for indicating and warning insufiicient brightness ofan object being photographed, and expog gg sure measuring circuitconnectable to said brightness indica- E 53 3 n M's/24] tor circuit andflash ready indicator for a flash exposure,

whereby an indicator in said brightness indicator circuit in- [56]References Cited structs a camera operator to use a flash device andsaid flash indicator assures camera operator to get a correct flashexpo- UNITED STATES PATENTS sure- 3,526,177 9/1970 Kiper et al ..95/53EA 12 Claims, 5 Drawing Figures L/6/1/7' DEV/Cf CONT/POL C/PCU/ TPATENIED L W 3.678.828 sum 1 nr 3 1/6/47 DEV/CE CONTPOL C/PCU/ 7'INVENTORS YUKIO M AsHIMO BY MITSUO ISHIKAWA (magi 00071 ATTORNEYSminnows I912 3318.828 sum 2 ur 3 L IGHT DEV/CE 1 2 I7 CONT FOL CY/QC'U/TINVENTOR vumo HASH IMO M ITSUO ISHI KAWA myawmm ATTORN EYS PlTBlTEflJuwssen 3.678.828

sum 3 or 3 FIG.3

LIGHT DEV/C5 ALARM c/ecu/r FIG. 4

ALA-J- L/GHT DEV/CE- 6 1- Al F I\ nr wunem CIRCUIT '7 a FIG. 5

LIGHT DEV/CE- ALARM CIRCUIT W arm Ema ATTORNEYS EXPOSURE CONTROL DEVICEFOR A CAMERA The present invention relates to an indicator device foruse in cameras having an electronic shutter, and more particularly tosuch a device for indicating, preferably within the finder of a camera,whether or not the use of a speed light device is needed, completion ofthe charging of the speed light device and the range of interlocking ofthe speed light device.

In the prior art, where it is desired to take pictures by a camerahaving an electronic shutter with a flash light, the shutter circuit isswitched to a flash photographing position, and the photographing iseffected upon illumination of a neon lamp indicating the completion ofcharging of the main capacitor provided in the speed light device. Incase of cameras of the type having a fiash-auto device in which a properphotographing distance is established and thereby the diaphragm apertureis automatically determined, they oflen do not have an alarm unit toindicate that the adjustment made is outside the range of interlocking,e.g. an alarm unit for close distance, thereby resulting in an over orunder-exposure to cause inconveniences.

According to the present invention, the voltage across the maincapacitor of a speed light device is detected to provide the indicationof the completion of charging of the main capacitor as well as an alarmfor any setting outside the range of interlocking with the flash-autodevice in a convenient manner.

It is a primary object of the present invention to provide a brightnessindicator device which instructs an operator to use a speed light devicewhen the amount of light from an object being photographed is below agiven level.

It is another object of the present invention to provide an indicatordevice which indicates the completion of charging of the main capacitorof a speed light device.

It is a further object of the present invention to provide a device forindicating that photographing informations set is outside the range ofinterlocking of a speed light device.

Above and other objects, features and advantages of the invention willbecome apparent from the following description with reference to thedrawings, in which:

FIG. I is a schematic view of a first embodiment of the device accordingto the present invention, the device being in its position to determinethe amount of light from an object being photographed;

FIG. 2 is a similar view to FIG. I, but showing the device in itsposition at the full open of shutter operation;

FIG. 3 is a circuit diagram of a second embodiment of the deviceaccording to the present invention;

FIG. 4 is a circuit diagram of a third embodiment of the deviceaccording to the present invention, and

FIG. 5 is a circuit diagram of a fourth embodiment of the deviceaccording to the present invention.

Referring to the drawings, reference numeral 1 denotes a speed lightdevice of conventional design which includes a main capacitor (notshown), the voltage across which appears across terminals and b whensuch speed light device I is mounted on the body of a camera (notshown), one of the terminals a is connected with the base of an n-p-ntransistor, while the other terminal I; is connected with the emitter ofthe transistor 2. The collector of the transistor 2 is connected througha lamp 3 and a resistor 4 to a power source 19 to complete a chargingcompletion indicator circuit, the resistor 4 being used to incorporateflash light photographing informations as will be mentioned later.Reference numeral denotes a hotoconductor element which is arranged tobe connected across the charging completion indicator circuit. Referencenumeral 6 denotes a change-over switch between flash light hotographingcontact E and automatic photographic contact A. The changeover switch 6is constructed to have its movable contact normally connected with thecontact F, but to move the movable contact into connection with thecontact A when the shutter lever 25 is depressed. The contact F isconnected to an alarm circuit to be described later, while the contact Ais connected to a capacitor 7 which constitutes the time constantcircuit of the electronic shutter together with the photoconductorelement 5.

Reference numeral 8 denotes a start switch which is connected across thecapacitor 7 and which is adapted to be moved to its open positionsimultaneously with the actuation of the shutter mechanism to bedescribed later. Reference numeral 9 denotes a bias resistor for thetransistor 2. Reference numerals l0 and I1 denote transistors whichtogether constitute an alarm circuit, in the form of a Schmidt trigger,for example, which is operated by a voltage provided by a bleedercircuit comprising the photoconductor element 5 and the resistor 9.Reference numerals l2, l3, l4 and I5 denote resisters used in this alarmcircuit, and 16 a warning lamp which is illuminated when the transistor11 is on. A block designated by numeral 17 denotes an electronic shuttercontrol circuit connected in parallel with the capacitor 7. Referencenumeral 18 denotes an electromagnet which operates by the output of thecontrol circuit 17 to cause closure of the shutter mechanism to bedescribed later. Reference numeral [9 denotes a power switch which isclosed when the shutter lever is depressed. Members designated bynumerals 20 to 24 together constitute a mechanism for deciding theresistance of the resistor 4. Specifically, numeral 20 denotes adistance setting ring, 2] a cam on the ring 20, 22 denotes a contactwhich is movable around a pivot 23 in association with the cam 21, and24 denotes a film sensitivity adjusting ring carry ing on its uppersurface a base plate having a copper foil C printed thereon. The copperfoil C is arranged and shaped in such a way that when the contact 22moves in association with the setting of the distance on the ring 20,the resistance of the resistor 4 increases in case of a shootingdistance below a minimum shooting distance and in case of a shootingdistance beyond a maximum shooting distance.

Reference numerals 25 to 66 denote various members used to constitute ashutter mechanism. Specifically, numeral 25 denotes a shutter releaselever P which is resiliently urged upward by a spring 27 on end of whichis attached to the camera body P and the other end of which is attachedto the projection 26 on the lever 25. Reference numeral 28 denotes an msulating dowel disposed on the projection 26 of the shutter releaselever 25, the dowel 28 being operable to close the power switch 29 inresponse to the first stage of depression of the shutter release lever25 and to change over the switch 26 in response to the second stage ofsuch depression. Thus a movable contact 290 of the power switch 29 issecured to the top side of the dowel 28 so as to be moved into contactwith the contact stationary contact 29b to thereby close the powerswitch 29 when the shutter release lever 25 is depressed. Disposed belowthe dowel 28 is a movable contact 60 of the change-over switch 6 whichis normally in contact with the contact F. At the time when the switch29 is closed, a suitable spacing is provided between the dowel 28 andthe movable contact 60 of the change-over switch 6 so that the switch 6is switched from the contact F to the contact A at a small intervalafter the complete closure of the power switch 29. An elongate slot 30is formed in the shutter release lever 25 for cooperation with a guidemember 31 fixed on the camera body F to guide the vertical movement ofthe shutter release lever 25. Another dowel 32 is formed on the shutterrelease lever 25 to start the actuation of the shutter concurrently withthe change-over of the switch 6 from the contact F to the contact A. Alever 35 having a hook-shaped detent 34 at its forward end is rotatablymounted on the camera body by means of a pivot 35. A spring 36 abuttingagainst a stop 37 urges the lever 33 to rotate clockwise. A crank wheel38 is rotatably mounted on the camera body by means of a pivot 39 and isurged to rotate clockwise by a spring 40 abutting against pins 41 and42. A projection 43 formed on the cam wheel 38 engages the hook portion34 of the lever 33 when the setting of the shutter is effected. A crankshaft 44 is mounted on the pin 42 of the crank wheel 38 and is urgedupward by a spring 46 which is wound around a bolt 45 and abuts againstpins 47 and 48. The crank shaft 44 is provided with a notch 49 in whichengages the interlocking portion 51 of a shutter ring 50. The shuttermechanism includes a plurality of shutter blades, only one being shownby the numeral 52. The shutter blades such as 52 are rotatably carriedby pivots 53. As is usual, a guide slot 54 is formed in the shutterblade 52 for cooperation with a guide pin 55 secured to the shutter ring50, the arrangement being such that as the shutter ring 50 rotatesclockwise, the shutter blade 52 rotates counter-clockwise around thepivot 53, thereby opening the shutter. Another projection 56 is formedon the crank wheel 38 and serves to retain the shutter open. A thirdprojection 57 on the crank wheel 38 serves for the positioning, when thesetting of the shutter is effected, of a magnet driven member 58 to bedescribed later. A pair of stoppers 59 and 60 are provided to interruptthe rotation of the crank wheel 38. The magnet driven member 58comprises a cruciform control portion 61 and a magnet attracted portion61' integrally connected together by a pivot 62. The magnet drivenmember 58 is pivotally mounted on the camera body P at 63 and is urgedto rotate clockwise by a spring 64 with its one end secured to thecamera body P. The shutter ring 50 is urged counter-clockwise by aspring 65. The shutter ring 50 has a pin 67 thereon which is arranged toclose synchro-contacts 66 when the shutter reaches its fully openposition. These contacts are connected with the terminals c and d of thespeed light device.

The speed light device according to the present invention operates asfollows.

In response to the first stage of depresion of the shutter release lever25, the power switch 29 is closed, whereby a voltage from the bleedercircuit comprising the photoconductor element 5 and the resistor 9 isapplied to the base of the transistor to. If the amount of light from anobject being photographed is sufficiently high, the photoconductorelement 5 has a low value of resistance. Hence the voltage appiied tothe base of the transistor 10 is high enough to cause conduction of thistransistor, thereby turning the transistor 11 off. As a result, thewarning lamp l6 connected in series with the transistor 11 is notilluminated. If this is the case, the photographer continues thedepression of the shutter release lever 25 to its second stage, therebyeffecting the change-over of the switch 6 from the contact F to thecontact A. Concurrently with the change-over of the switch 6, the dowel32 on the lever 25 causes a counter-clockwise rotation of the lever 33,thereby releasing the crank wheel 38 from detent by the hook portion 34of the lever 33 and causing the wheel 38 to rotate clockwise under theaction of the spring 40 until it is engaged with and held by thecruciform control portion 61 of the magnet driven member 58 (see FIG.2). As the crank wheel 38 rotates, the crank shaft 44 starts its crankmotion. This allows the shutter ring 50 to rotate clockwise, whereby theguide pin 55 thereon causes the shutter blades 52 to rotate clockwisearound their pivots 53, thereby opening the shutter. Simultaneously withthe start of rotation of the shutter ring, the start switch 8 is opened,thereby permitting the time constant circuit comprising thephotoconductor element 5 and the capacitor 7 to initiate its integratoraction. During the time when the time constant circuit is continuing itscharging, the shutter control circuit 17 operates to maintain theelectromagnet l8 energized, so that the magnet attracted portion 6! isheld attracled to cause the mechanism 38, 44 to keep the fully openposition ofthe shutter.

Upon termination of the timing control by the time constant circuits 5and 7, and the electronic shutter control circuit 17, the electromagnetis deenergized to discontinue its attraction upon the magnet drivenmember 58 and to release the latter, whereupon the member 58 rotatesclockwise about the pivot 63 under the action of the spring 64. Thisrotation of the member 58 permits the crank wheel 38 to rotate againclockwise until the member 58 engages the stopper 59. Such rotation ofthe crank wheel 38 is transmitted through the crank shaft 44 to cause acounter-clockwise rotation of the shutter ring 50, thereby closing theshutter blades. After the shutter is once operated to take a picture, itis reset by a counter-clockwise rotation of the crank wheel 38 until thewheel 38 engages the stopper 60, for example, by interlocked motion witha film winding mechanism.

When the amount of light from an object being photographed is small, thephotoconductor element 5 has a high value of resistance, so that thevoltage input to the transistor 10 of the alarm circuit is insufficientto cause the conduction thereof. As a result, the transistor ll conductsto illuminate the warning lamp l6. By the illumination of the lamp 16,the operator is advised of the need to mount a speed light device 1 onthe camera. The switch in the speed light device I turned on to initiatethe charging of the main capacitor therein. The completion of chargingof the main capacitor in the device I is indicated by an indicator lampin response to a voltage across the terminals a and b which is highenough to cause the conduction of the transistor 2, whereupon theindicator lamp 3 is illuminated. In this manner, an indication as to thecompletion of charging of the speed light device 1 is transferred intothe camera body, preferably to the finder thereof. Then the operator maydepress the shutter release lever 25 to its first stage, whereby thepower switch 19 is closed. It is to be noted that at this time, thephotoconductor element 5 is shunted by the charging completion indicatorcircuit 2, 3, 4, and that these parallel paths operate selectively. Thusif the camera is spaced close to or at a great distance from an objectbeing photographed, the resistor 4 takes a high value of resistance sothat the charging completion indicator circuit 2, 3, 4 cannot operate,but the alarm circuit operates to illuminate the warning lamp [6. Whenthe operator modifies a photographing in formation, the warning lamp 16is extinguished and the charging completion indicator lamp 3 isilluminated.

Upon illumination of the lamp 3, the operator further depresses theshutter release lever 25 to its second stage, whereby the switch 6 isswitched from the contact F to the contact A and the shutter mechanismoperates as mentioned before. When the shutter reaches its fully openposition, the pin 67 on the shutter ring 50 operates to close thesynchrocontacts 66 to feed a synchro-signal through the terminals c, dto the speed light device 1, which device is then operated forillumination.

The second embodiment shown in FIG. 3 is similar to the first embodimentjust described, except that the charging completion indicator lamp 3 isreplaced by an electromagnetic relay comprising an electromagnet 68having an associated switch 69 which is connected in series with aresistor 70 to shunt the photoconductor element 5 and that the resistor4 is replaced by a switch 71 which is opened in case of a shootingdistance below a minimum shooting distance and in case of a shootingdistance beyond a maximum shooting distance. In operation, the voltageacross the main capacitor in the speed light device 1 controls thetransistor 2, and when this voltage becomes sufiicient for illuminationof the device I, the electromagnetic relay 68, 69 is energized toconnect the resistor 70 in parallel with the photoconductor element 5 ofthe electronic shutter circuit, thereby decreasing the resultantresistance to cause illumination of the warning lamp l6 to indicate thatthe speed light device 1 is ready for illuminating operation. A warningagainst a setting outside the range of interlocking with the flash-autodevice is provided by turning the switch 71 off to extinguish thewarning lamp through interlocked motion of the switch 71 with aphotographic information setting.

In the third embodiment shown in FIG. 4, the electromagnetic relay shownin FIG. 3 is replaced by a small lamp 72 optically arranged toilluminate the photoconductor element 5 in case when the speed lightdevice with the lamp 72 is clipped on the camera. With this arrangement,the lamp 72 is connected to be fed from the power sources within thespeed light device, and when illuminated, the lamp 72 providesadditional light input to the element 5 for operating the alarm circuitAl and the shutter circuit (not shown).

In the fourth embodiment shown in FIG. 5, the output from the speedlight device 1 is used to operate an electromagnetic relay whichoperates onto an element, other than the photoconductor element, of thealarm circuit. In the example shown, the relay operates a change-overswitch 73 to connect a resistor 74 of higher resistance than that of theresistor 9 in the circuit in order to indicate that the speed lightdevice is ready for operation by illuminating the warning lamp 16.

From the foregoing, it will be understood that the invention provides anindicator device capable of indicating the ready condition of a speedlight device used in taking pictures by flash light and of giving anindication the operable range of the electronic shutter circuit. Inaddition, by combining these functions in an interlocked device, awarning can be given to indicate that a setting made is outside therange of interlocking when taking pictures by flash light. Moreover,these indicator lamps can be preferably mounted within the finder of aphotographic camera to facilitate taking pictures by flash light.

What is claimed is:

I. An apparatus for indicating satisfactory operating conditions for acamera, comprising indicating means for producing indication thatdistinguish between sufficient and insufficient light, said indicatingmeans including light sensing means and an indicator responsive to saidlight sensing means, auxiliary light producing means capable ofproducing auxiliary light, said auxiliary light producing means having alight source, said auxiliary light producing means having actuable andvariable power means for energizing said source when said power meansreaches a given power state and when said power means is actuated, saidpower means generating a given electrical value when said power meansreaches the given power state, and control means connected to saidindicating means for varying the response of said indicating means andrendering said indicating means responsive to the given electricalvalue.

2. An apparatus, as in claim I, wherein the camera includes variablesettings, and wherein said control means include regulating meansresponsive to said setting for operating said indicating means inresponse to said regulating means.

3. An apparatus, as in claim 1, wherein said control means includes alamp connected to said power means to respond to the indication, saidsensing means being exposed to said lamp so as to effect the variationin the response of said indicating means.

4. An apparatus, as in claim I, wherein said control means includes amagnet responsive to said power means and a switch connected to saidsensing means for varying the response of said indicator to said sensingmeans.

5. An apparatus for indicating satisfactory operating conditions for acamera, comprising a photoconductive member exhibiting varying impedancevalues in response to variation in the light to which it is exposed, anexposure alarm control circuit having an input circuit connected to saidphotoconductive means, alarm indicating means connected to respond tosaid exposure alarrn control circuit, said control circuit beingactuated by a predetermined actuating level depending upon the impedanceof said photoconductive means, an auxiliary light, a power source forsaid auxiliary light, said power source producing a voltage to indicatereadiness to operate said source, a detecting circuit for indicatingproper operating conditions of said source, and coupling means in saiddetecting circuit connected to said input circuit for varying theeffective input to a level lower than the actuating level.

6. An apparatus, as in claim 5, wherein said coupling means includes atransistor having a base circuit responsive to said detecting circuitand emitter-collector circuit, a lamp in series with saidemitter-collector circuit and positioned to expose said photoconductivemember to the light therefrom, said transistor being poled to reduce theimpedance of said emitter-collector path in response to an indicationfrom said detecting circuit of proper operating conditions for saidsource.

7. An apparatus, as in claim 5, wherein said coupling means includesresistance means connected to said input circuit so as to vary theeffect of said photoconductive member upon the operation of said inputcircuit, switch means in series with said resistance means, andelectromagnetic means responsive to said indicating means for operatingsaid switch means.

8. An apparatus, as in claim 5, wherein said coupling means includesluminous means optically coupled with said photoconductive member andresponsive to said detecting circuit so as to be actuated thereby andreduce the impedance of the photoconductive member.

9. An apparatus, as in claim 5, further comprising setting means forsaid camera, said detecting circuit including a variable impedanceelement responsive to said setting means, said setting means beingeffective to change the focus of said camera, said element beingeffective to change said detecting circuit to indicate an inoperativecondition when said element is moved by said setting means to extremepositions.

10. An apparatus, as in claim 7, wherein said resistance means and saidswitching means form a series circuit connected parallel to saidphotoconductive member H. An apparatus, as in claim 7, wherein saidresistance means includes a high resistance element and a low resistanceelement, said switching means being connected alternately in series witheach of said resistance elements in response to said electromagneticmeans.

12. An apparatus, as in claim 8, wherein said luminous means comprisesan electric lamp serving as an indication member for indicating a properoperating condition for said auxiliary light.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3678,8Z8 Dated July 25, 1972 Inventor(s) Yukio Mashimo, et. a1.

It is certified that error appears in the above-identified patent andthat said Letters Patent are hereby corrected as shown below:

In the grant only, insert the attached two sheets of drawing.

Signed and sealed this 8th day of May 1973.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissionerof Patents FORM PC4050 (10-69) USCOMM-DC scan-Poo U45 GOV ERNHENYPRINTING OFFICE! l9, '355'33,

PAIENTEDJULZS m 4 3.578.828 sum 2 or 3 LIGHT DEV/Cf I1 CONTROL C/PCU/TINVENTORS YUHIO HHSFHHO M ITSUO 26m KAWA m wa/mfinm ATTORNEYS LIGHTDEV/CE SHEEI 3 BF 3 "ALARM c/zcu/ r FIGJ.

l j LIGHT DEV/CE- A I f}- V ALARM cmcu/T 7 9 FIG.

LIGHT DEV/CE ALARM CIRCUI T INVENTORS Yuma MASHIMO HITSUO ISHIRAWAORNEYS zf lw ama 761m

1. An apparatus for indicating satisfactory operating conditions for acamera, comprising indicating means for producing indication thatdistinguish between sufficient and insufficient light, said indicatingmeans including light sensing means and an indicator responsive to saidlight sensing means, auxiliary light producing means capable ofproducing auxiliary light, said auxiliary light producing means having alIght source, said auxiliary light producing means having actuable andvariable power means for energizing said source when said power meansreaches a given power state and when said power means is actuated, saidpower means generating a given electrical value when said power meansreaches the given power state, and control means connected to saidindicating means for varying the response of said indicating means andrendering said indicating means responsive to the given electricalvalue.
 2. An apparatus, as in claim 1, wherein the camera includesvariable settings, and wherein said control means include regulatingmeans responsive to said setting for operating said indicating means inresponse to said regulating means.
 3. An apparatus, as in claim 1,wherein said control means includes a lamp connected to said power meansto respond to the indication, said sensing means being exposed to saidlamp so as to effect the variation in the response of said indicatingmeans.
 4. An apparatus, as in claim 1, wherein said control meansincludes a magnet responsive to said power means and a switch connectedto said sensing means for varying the response of said indicator to saidsensing means.
 5. An apparatus for indicating satisfactory operatingconditions for a camera, comprising a photoconductive member exhibitingvarying impedance values in response to variation in the light to whichit is exposed, an exposure alarm control circuit having an input circuitconnected to said photoconductive means, alarm indicating meansconnected to respond to said exposure alarm control circuit, saidcontrol circuit being actuated by a predetermined actuating leveldepending upon the impedance of said photoconductive means, an auxiliarylight, a power source for said auxiliary light, said power sourceproducing a voltage to indicate readiness to operate said source, adetecting circuit for indicating proper operating conditions of saidsource, and coupling means in said detecting circuit connected to saidinput circuit for varying the effective input to a level lower than theactuating level.
 6. An apparatus, as in claim 5, wherein said couplingmeans includes a transistor having a base circuit responsive to saiddetecting circuit and emitter-collector circuit, a lamp in series withsaid emitter-collector circuit and positioned to expose saidphotoconductive member to the light therefrom, said transistor beingpoled to reduce the impedance of said emitter-collector path in responseto an indication from said detecting circuit of proper operatingconditions for said source.
 7. An apparatus, as in claim 5, wherein saidcoupling means includes resistance means connected to said input circuitso as to vary the effect of said photoconductive member upon theoperation of said input circuit, switch means in series with saidresistance means, and electromagnetic means responsive to saidindicating means for operating said switch means.
 8. An apparatus, as inclaim 5, wherein said coupling means includes luminous means opticallycoupled with said photoconductive member and responsive to saiddetecting circuit so as to be actuated thereby and reduce the impedanceof the photoconductive member.
 9. An apparatus, as in claim 5, furthercomprising setting means for said camera, said detecting circuitincluding a variable impedance element responsive to said setting means,said setting means being effective to change the focus of said camera,said element being effective to change said detecting circuit toindicate an inoperative condition when said element is moved by saidsetting means to extreme positions.
 10. An apparatus, as in claim 7,wherein said resistance means and said switching means form a seriescircuit connected parallel to said photoconductive member
 11. Anapparatus, as in claim 7, wherein said resistance means includes a highresistance element and a low resistance element, said switching meansbeing connected alternately in series with each of said resistanceelements in response to saiD electromagnetic means.
 12. An apparatus, asin claim 8, wherein said luminous means comprises an electric lampserving as an indication member for indicating a proper operatingcondition for said auxiliary light.